The invention is related to a fuel tank control for controlling excess fuel in a motor vehicle having at least two fuel tanks.
Typically, diesel trucks, such as tractor trailors, have two fuel tanks. Each fuel tank has its own fuel pump. A manual or automatic switch is used to control from which fuel tank the fuel is taken. The fuel is then pumped by the trucks fuel pump to the motor.
A fuel injected diesel motor, for example, does not use all of the fuel that is supplied by the fuel pump of the individual tank. The excess fuel must be removed from the injection system of the motor and returned to one of the two fuel tanks. Preferably, the fuel is returned to the fuel tank from which the fuel is taken in order to avoid overflow in a full tank. Typically this is done through a return line that is connected to a valve. The valve operates to allow the fuel to return to only one of the two fuel tanks, preferably to that tank from which the fuel was originally taken from.
Typically, there are two switches in the cab of the truck, one to select the fuel tank, and one to select the tank for the return fuel. A frequent problem has been the operator forgetting to switch both switches so that the excess fuel is returned to a full tank instead of the tank that is being emptied. This causes overflow or fuel backup problems.
One solution to the manual control has been the electronic control. That is, when the operator in the truck cab manually switches from one tank to the other, an electronic switch switches the return fuel line as well. A problem with electronic switches is that they can fail and ultimately cause the same backup and overflow problems.
It is desirable to have a fuel return control system that does not rely on either manually operated switches or electronic switches to feed the excess fuel to the appropriate fuel tank.
The invention is directed to a fuel tank control for tractor trailers for recovering excess fuel delivered to the fuel injectors. The system uses a spool valve that is switched over from draining excess fuel from one tank to the other tank when the supply is switched over. The fuel delivery pressure biases the valve to the proper side for return flow to the appropriate tank.
In particular, the invention is directed to a fuel tank control for controlling excess fuel to an engine of a vehicle having at least two fuel tanks. The first fuel tank has a first fuel pump and a second fuel tank has a second fuel pump. A first fuel supply line is connected to an outlet of the first fuel pump, a second fuel supply line is connected to an outlet of the second fuel pump. Each of the first fuel supply line and second fuel supply line is connected to supply pressurized fuel to an injection system of the vehicle engine and fuel pressure to a control valve. A switch controls which fuel pump is operated. A fuel return line is connected to the motor to receive excess fuel and connected to a valve having an internal spool including at least one passage to regulate which tank the fuel is to be returned. When the first fuel pump is operated, the spool is translated to position a passage to return the excess fuel to the first fuel tank via a first outlet line and when the second fuel pump is operated, the spool is translated to position a passage to return the excess fuel to the second fuel tank through a second outlet line.
These features of the invention will be apparent upon consideration of the following detailed description thereof, presented in connection with the following drawings in which like reference numerals identify the elements throughout.